In human hearing, hair cells in the cochlea respond to sound waves and produce corresponding auditory nerve impulses. These nerve impulses are then conducted to the brain and perceived as sound.
Hearing loss, which may be due to many different causes, is generally of two types: conductive and sensorineural. Conductive hearing loss typically occurs where the normal mechanical pathways for sound to reach the hair cells in the cochlea are impeded, for example, from damage to the ossicles. Conductive hearing loss may often be helped by using conventional hearing aids that amplify sounds so that acoustic information can reach the cochlea and the hair cells. Some types of conductive hearing loss are also amenable to alleviation by surgical procedures.
Many people who are profoundly deaf, however, have sensorineural hearing loss. This type of hearing loss can arise from the absence or the destruction of the hair cells in the cochlea which then no longer transduce acoustic signals into auditory nerve impulses. Individuals with sensorineural hearing loss are unable to derive any benefit from conventional hearing aid systems no matter how loud the acoustic stimulus is. This is because the mechanism for transducing sound energy into auditory nerve impulses has been damaged. Thus, in the absence of properly functioning hair cells, auditory nerve impulses cannot be generated directly from sounds.
To overcome sensorineural deafness, cochlear implant systems or cochlear prostheses have been developed that can bypass the hair cells located in the vicinity of the radially outer wall of the cochlea by presenting electrical stimulation directly to the auditory nerve fibers. This leads to the perception of sound in the brain and provides at least partial restoration of hearing function. Thus, most of these cochlear prosthesis systems treat sensorineural deficit by stimulating the ganglion cells in the cochlea directly using an implanted electrode or lead that has an electrode array. Thus, a cochlear prosthesis operates by directly stimulating the auditory nerve cells, bypassing the defective cochlear hair cells that normally transduce acoustic energy into electrical activity to the connected auditory nerve cells.
Prior to stimulating the nerve cells, the electronic circuitry and the electrode array of the cochlear prosthesis separate acoustic signal into a number of parallel channels of information, each representing a narrow band of frequencies within the perceived audio spectrum. Ideally, each channel of information should be conveyed selectively to a subset of auditory nerve cells that normally transmit information about that frequency band to the brain. Those nerve cells are arranged in an orderly tonotopic sequence, from the highest frequencies at the basal end of the cochlear spiral to progressively lower frequencies towards the apex.
A wide variety of electromechanical devices may be used to treat the various causes of hearing loss. Such devices include, but are not limited to, in-the-ear hearing aids, Behind-The-Ear (BTE) hearing aids, bone conduction hearing aids, body worn, BTE and otherwise external sound processing units, and cochlear implants. A cochlear prosthesis, for example, may typically comprise both an external unit that receives and processes ambient sound waves and an implant that receives data from the external unit and uses that data to directly stimulate the auditory nerve. As used herein, the term “hearing assistance device” is used generally to refer to any of these devices, including hearing aids and external sound processing units that supply data to cochlear implants, that are used to treat all of the various forms of hearing loss.
Hearing assistance devices are typically worn regularly and over a significant period of each day. Consequently, the assistive devices must be robust and reliable. Additionally, the assistive devices should be visually unobtrusive and not unduly restrict the user's activities. Many of these assistive devices have one or more external controls which allow for a number of adjustments to the operation of the device or its processor, such as volume, sensitivity, and program settings.
The present inventors have determined that, while the external controls are important to the proper and comfortable use of the device, they tend to be infrequently needed and may also create a number of issues. For example, external controls can increase the size of the hearing assistance device. Control knobs also take up space and add to the overall size of the device. This makes the device more visible and conspicuous and may make its wearer more self-conscious. External controls can also be weak points which allow the ingress of contaminants and water into the device. If a seal fails on one of the controls, the integrity of the processor could be compromised and the processor would need to be sent back to the manufacturer for repair. External controls can also be easily bumped and moved, resulting in unwanted adjustments to the operation of the device. In particular, children wearing one of these devices may be prone to inadvertently actuating the external controls of a hearing assistance device while at play. A child may also innocently, but intentionally, operate the controls of the hearing assistance device and change the settings without a parent being aware.
Throughout the drawings, identical reference numbers designate similar, but not necessarily identical, elements.